The ISL6506 complements other power building blocks (voltage regulators) in ACPI-compliant designs for microprocessor and computer applications. The IC integrates the control of the 5VDUAL and 3.3VDUAL rails into an 8 pin EPAD SOIC package. The ISL6506 operating mode (active outputs or sleep outputs) is selectable through two digital control pins, S3# and S5#. A completely integrated linear regulator generates the 3.3VDUAL voltage plane from the ATX supply's 5VSB output during sleep states (S3, S4/S5). In active states (during S0 and S1/S2), the ISL6506 uses an external N-channel pass MOSFET to connect the outputs directly to the 3.3V input supplied by an ATX power supply, for minimal losses. The ISL6506 powers up the 5VDUAL plane by switching in the ATX 5V output through an NMOS transistor in active states, or by switching in the ATX 5VSB through a PMOS (or PNP) transistor in S3 sleep state. In S4/S5 sleep states, the ISL6506 and ISL6506B 5VDUAL output is shut down. In the ISL6506A, the 5VDUAL output stays on during S4/S5 sleep states.